This invention relates to the preparation of aromatic thiols.
Aromatic thiols such as thiophenols are well known compounds with a variety of commercial uses. These compounds are used in pharmaceutical synthesis, as a rubber plasticizer, in the reclaiming of rubber, and in the manufacture of insecticides and agro-chemicals.
The preparation of aromatic thiols is also well known in the art. Spainhour (U.S. Pat. No. 3,374,274) teaches preparing aromatic thiols and sulfides by reacting a nuclear monohalo substituted compound with an excess of an alkali metal sulfide. Louthan (U.S. Pat. No. 3,415,889) discloses the preparation of aromatic heterocyclic thiols by reacting an alkali metal sulfide with polyhalo compound(s), in the presence of a polar organic compound solvent. Furthermore, Thies (U.S. Pat. No. 4,209,469) teaches the production of aryl thiol by hydrogenating an aryl sulfur chloride in a protic or aprotic solvent in the presence of platinum as a catalyst. Of more relevance to the present invention is the disclosure by Testaferri et al. (Syntheses 1983 at page 752) showing the preparation of aromatic thiols by reacting an aryl halide with sodium alkanethiolate using N,N-dimethylformamide (DMF) as a solvent.
This invention differs from the Testaferri et al. method in, at least, the following respects. First, unlike the Testaferri et al. method, this invention works well when alkyl substituted aryl halides are used. Second, in this invention, the undesired loss of sodium alkanethiolate, an essential intermediate reactant, does not occur. Third, the rate of the reaction is significantly increased by the method of this invention.
In a nutshell, the present invention represents an improved, simple and inexpensive "one pot reaction" process for the preparation of aromatic thiols in the desired purity and yield.